The present invention generally relates to large electronic systems, and in particular, to a telecommunications switching system configuration that does not require a common switch fabric board.
Large electronic systems, as used in computing, data networking, and telecommunications elements often use a common backplane to provide high speed interconnection between several circuit boards, packs or modules that plug into slots in the backplane. The backplane is typically constructed of a multi-layer circuit board with conductive traces selectively routed to provide the high-speed interconnection. Connectors are provided on the backplane to couple circuit boards, packs, or modules which are held in place using a slotted chasis. The properties of these backplanes often have large influence over the capacity, performance, reliability, cost, and scale properties of electronic systems. Some backplane designs provide high capacity, while others provide low cost.
Currently, there are two predominant architectures for providing backplane transport infrastructures in high-speed telecommunications platforms, the bus and the fabric. These architectures both have limitations preventing the creation of a truly universal platform.
Bus-based backplanes use a large set of parallel signals, where each signal typically touches each slot and hence each board. This interconnection scheme is versatile and low cost, but imposes practical limits of a few billion bits per second on the maximum system throughput and also limits reliability. The total throughput must also be shared among all boards on the backplane. Buses are typically used in smaller systems that do not process large amounts of broadband traffic, or in systems with severe cost constraints. In particular, bus-based backplanes have a very low cost of common elements, and therefore permit low system costs, especially where a system is not equipped with all of its circuit cards or modules initially.
Fabric based systems use a central high-speed fabric or hub to switch traffic between all modules. High-speed point-to-point connections (either parallel or serial) are routed over a cable or backplane between each module and the central fabric, in a star topology. The central fabric can provide the large bandwidths (over 1 trillion bits per second) needed to support high-speed computing or broadband communications. Unfortunately, because the full central fabric, with support for the maximum number of connections, must be installed before any modules can be interconnected, the cost of such a system is often quite high, especially for partially equipped systems, where the large cost of the fabric is only amortized over a few modules.
Computing and telecommunications needs are increasing tremendously. In particular, high bandwidth systems are considered a necessity for distributed computing, networking and telecommunications switching. In light of the shortcomings of traditional bus-based backplane systems and central fabric-based systems, a need exists for a new paradigm in backplane-based systems that has the low cost of bus-based interconnect and the high capacity of central fabric-based interconnect.
An electronic interconnection system in accordance with the present invention includes a backplane. The backplane includes a multi-layer circuit board with a plurality of connectorized slots for connecting to traces routed in the backplane. Using the connectorized slots, circuit packs are coupled to the backplane and traces routed therein. To facilitate communication among the circuit packs coupled to the backplane, a hub circuit is provided on each circuit pack. In addition, point-to-point connections are provided from one slot in the backplane to each and every other slot in the backplane. The point-to-point connections are made using traces in the backplane. The hub circuits on each circuit pack couple to the point-to-point connections to facilitate control and routing over the communication links formed by the point-to-point connections.
The point-to-point connections formed in the backplane can be selectively routed between the slots, either physically or virtually, using the hub circuit to provide different connection topologies, capacity, and reliability. In one configuration, each slot includes a point-to-point connection to all other slots, creating a full mesh. For example, for a backplane with sixteen slots for circuit boards, each board has fifteen point-to-point connections, each terminating at a different slot. This configuration provides a direct point-to-point connection from any one circuit pack or module to another circuit pack or module. In addition, communication between circuit packs is readily facilitated by communication through another circuit pack, if for example, a point-to-point connection is faulty or unavailable. A myriad of other configurations are contemplated, including a ring configuration, wherein adjacent slots have point-to-point connections and slots at opposite ends are joined via point-to-point connections to complete the ring.